Solid electrolyte material, lithium battery, and method of producing solid electrolyte material

ABSTRACT

A main object of the present invention is to provide a solid electrolyte material having excellent Li ion conductivity. To attain the object, the present invention provides a solid electrolyte material represented by a general formula: Li x (La 1-a M1 a ) y (Ti 1-b M2 b ) z O δ , wherein “x”, “y”, and “z” satisfy relations of x+y+z=1, 0.850≦x/(x+y+z)≦0.930, and 0.087≦y/(y+z)≦0.115; “a” is 0≦a≦1; “b” is 0≦b≦1; “δ” is 0.8≦δ≦1.2; “M1” is at least one selected from the group consisting of Sr, Na, Nd, Pr, Sm, Gd, Dy, Y, Eu, Tb, and Ba; and “M2” is at least one selected from the group consisting of Mg, W, Mn, Al, Ge, Ru, Nb, Ta, Co, Zr, Hf, Fe, Cr, and Ga.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of InternationalApplication No. PCT/JP2010/056607, filed Apr. 13, 2010, the contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a solid electrolyte material havingexcellent Li ion conductivity.

BACKGROUND ART

In accordance with a rapid spread of information relevant apparatusesand communication apparatuses such as a personal computer, a videocamera and a portable telephone in recent years, the development of abattery to be utilized as a power source thereof has been emphasized.The development of a high-output and high-capacity battery for anelectric automobile or a hybrid automobile has been advanced also in theautomobile industry. A lithium battery has been presently noticed fromthe viewpoint of a high energy density among various kinds of batteries.

Liquid electrolyte containing a flammable organic solvent is used for apresently commercialized lithium battery, so that the installation of asafety device for restraining temperature rise during a short circuitand the improvement in structure and material for preventing the shortcircuit are necessary therefor. On the contrary, a lithium batteryall-solidified by replacing the liquid electrolyte with a solidelectrolyte layer is conceived to intend the simplification of thesafety device and be excellent in production cost and productivity forthe reason that the flammable organic solvent is not used in thebattery.

An Li—La—Ti—O-based solid electrolyte material (LLT) has been known as asolid electrolyte material used for an all solid state lithium battery.For example, Patent Literature 1 discloses a solid electrolyte membranehaving lithium ion conductivity, in which the solid electrolyte membranehas a composition of La_(x)Li_(y)Ti_(z)O₃ (0.4≦X≦0.6, 0.4≦Y≦0.6,0.8≦Z≦1.2, Y<X) and is an amorphous structure.

Further, Patent Literature 2 discloses a solid electrolyte layercomposed of a solid electrolyte made of a complex oxide containing Li,La and Ti, in which the solid electrolyte layer has an amorphous layer,a crystalline layer and a lattice defective layer. In addition, inPatent Literature 2, it is described that the composition of a solidelectrolyte material is preferably La_(2/3-x)Li_(3x)TiO₃ (0.03≦x≦0.167).This solid electrolyte material is synthesized by performing planetaryball milling and burning, and corresponds to the so-called bulk body,not a thin membrane.

Further, Patent Literature 3 discloses a perovskite type complex oxiderepresented by Li_(x)La_(y)Ti_(z)O₃ (x, y, z satisfy 0.08≦x≦0.75,0.8≦z≦1.2, x+3y+4z=6, respectively). Further, in Examples of PatentLiterature 4, a lithium ion conductor represented byLi_(0.34)La_(0.51)TiO_(2.94) is disclosed. Further, in Examples ofPatent Literature 5, a perovskite type oxide represented byLi_(0.26)La_(0.57)TiO₃ is disclosed.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application Publication    Laid-Open (JP-A) No. 2009-238704-   Patent Literature 2: JP-A No. 2008-059843-   Patent Literature 3: JP-A No. H11-079746-   Patent Literature 4: JP-A No. H06-333577-   Patent Literature 5: JP-A No. H09-219215

SUMMARY OF INVENTION Technical Problem

A solid electrolyte material having excellent Li ion conductivity hasbeen demanded from the viewpoint of achieving higher output of abattery. The present invention has been made in view of theabove-mentioned actual circumstances, and a main object thereof is toprovide a solid electrolyte material having excellent Li ionconductivity.

Solution to Problem

To attain the object, the present invention provides a solid electrolytematerial represented by a general formula:Li_(x)(La_(1-a)M1_(a))_(y)(Ti_(1-b)M2_(b))_(z)O_(δ), characterized inthat “x”, “y”, and “z” satisfy relations of x+y+z=1,0.850≦x/(x+y+z)≦0.930, and 0.087≦y/(y+z)≦0.115; “a” is 0≦a≦1; “b” is0≦b≦1; “δ” is 0.8≦δ≦1.2; “M1” is at least one selected from the groupconsisting of Sr, Na, Nd, Pr, Sm, Gd, Dy, Y, Eu, Tb, and Ba; and “M2” isat least one selected from the group consisting of Mg, W, Mn, Al, Ge,Ru, Nb, Ta, Co, Zr, Hf, Fe, Cr, and Ga.

A solid electrolyte material having excellent Li ion conductivity may beobtained for the reason that the present invention has theabove-mentioned general formula. The solid electrolyte material of thepresent invention has so high lithium content as to have the advantagethat carrier concentration for contributing to Li ion conduction ishigh.

In the above-mentioned present invention, the solid electrolyte materialpreferably shows peaks in an X-ray diffraction measurement using CuKαwhere 2θ=22°, 27°, 34°, 35°. The reason therefor is that these peaks areconceived to derive from a crystal phase of high Li ion conductivity.

In the above-mentioned present invention, the solid electrolyte materialis preferably in thin film form. The reason therefor is that the minutesolid electrolyte material may be obtained and Li ion conductivity maybe improved.

In the above-mentioned present invention, the solid electrolyte materialpreferably has a thickness of 200 nm to 5 μm.

In the above-mentioned present invention, the “a” and the “b” arepreferably 0.

Further, the present invention provides a lithium battery comprising: acathode active material layer containing a cathode active material, ananode active material layer containing an anode active material, and asolid electrolyte layer formed between the cathode active material layerand the anode active material layer, characterized in that the solidelectrolyte layer contains the above-mentioned solid electrolytematerial.

According to the present invention, the use of the above-mentioned solidelectrolyte material allows a high-output lithium battery.

Further, the present invention provides a method of producing a solidelectrolyte material comprising steps of: preparing a raw material, inwhich the raw material is made of Li, La, Ti, M1 (M1 being at least oneselected from the group consisting of Sr, Na, Nd, Pr, Sm, Gd, Dy, Y, Eu,Tb, and Ba), and M2 (M2 being at least one selected from the groupconsisting of Mg, W, Mn, Al, Ge, Ru, Nb, Ta, Co, Zr, Hf, Fe, Cr, andGa); and forming a thin film, in which the solid electrolyte material isformed using the raw material to a substrate by a reactive depositionmethod using oxygen, and the solid electrolyte material is representedby a general formula:Li_(x)(La_(1-a)M1_(a))_(y)(Ti_(1-b)M2_(b))_(z)O_(δ), characterized inthat “x”, “y”, and “z” satisfy relations of x+y+z=1,0.850≦x/(x+y+z)≦0.930, and 0.087≦y/(y+z)≦0.115; “a” is 0≦a≦1; “b” is0≦b≦1; “δ” is 0.8≦δ≦1.2.

According to the present invention, the use of the reactive depositionmethod allows a minute thin film to be formed, and a solid electrolytematerial having excellent Li ion conductivity may be obtained by theabove-mentioned general formula.

In the above-mentioned present invention, the solid electrolyte materialpreferably shows peaks in an X-ray diffraction measurement using CuKαwhere 2θ=22°, 27°, 34°, 35°. The reason therefor is that these peaks areconceived to derive from a crystal phase of high Li ion conductivity.

In the above-mentioned present invention, the solid electrolyte materialpreferably has a thickness of 200 nm to 5 μm. The reason therefor isthat the minute solid electrolyte material may be obtained and Li ionconductivity may be improved.

In the above-mentioned present invention, the solid electrolyte materialis preferably formed in the thin film forming step by the reactivedeposition method using an oxygen plasma.

In the above-mentioned present invention, the substrate is preferably amember containing a cathode active material layer or an anode activematerial layer. The reason therefor is to be useful for producing alithium battery.

Advantageous Effects of Invention

The present invention produces the effect such as to allow a solidelectrolyte material having excellent Li ion conductivity.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a ternary view explaining a solid electrolyte material of thepresent invention.

FIG. 2 is a schematic cross-sectional view showing an example of alithium battery of the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of amethod of producing a solid electrolyte material of the presentinvention.

FIG. 4 is a result of XRD measurement of a solid electrolyte materialobtained in Example 1.

FIG. 5 is a result of XRD measurement of a solid electrolyte materialobtained in Comparative Example 1.

FIG. 6 is a result of measuring Li ion conductivity of solid electrolytematerials obtained in Examples 1 to 5 and Comparative Examples 1 and 2.

FIG. 7 is a ternary view explaining solid electrolyte materials obtainedin Examples 1 to 5 and Comparative Examples 1 and 2.

FIG. 8 is a result of measuring Li ion conductivity of solid electrolytematerials obtained in Examples 4, 6 to 9 and Comparative Examples 3 and4.

FIG. 9 is a ternary view explaining solid electrolyte materials obtainedin Examples 4, 6 to 9 and Comparative Examples 3 and 4.

FIG. 10 is a ternary view explaining solid electrolyte materialsobtained in Examples 10 to 15 and Comparative Examples 5 to 9.

DESCRIPTION OF EMBODIMENTS

A solid electrolyte material, a lithium battery and a method ofproducing a solid electrolyte material of the present invention arehereinafter described in detail.

A. Solid Electrolyte Material

A solid electrolyte material of the present invention is firstdescribed. A solid electrolyte material of the present invention isrepresented by a general formula:Li_(x)(La_(1-a)M1_(a))_(y)(Ti_(1-b)M2_(b))_(z)O_(δ), characterized inthat “x”, “y”, and “z” satisfy relations of x+y+z=1,0.850≦x/(x+y+z)≦0.930, and 0.087≦y/(y+z)≦0.115; “a” is 0≦a≦1; “b” is0≦b≦1; “δ” is 0.8≦δ≦1.2; “M1” is at least one selected from the groupconsisting of Sr, Na, Nd, Pr, Sm, Gd, Dy, Y, Eu, Tb, and Ba; and “M2” isat least one selected from the group consisting of Mg, W, Mn, Al, Ge,Ru, Nb, Ta, Co, Zr, Hf, Fe, Cr, and Ga.

A solid electrolyte material having excellent Li ion conductivity may beobtained for the reason that the present invention has theabove-mentioned general formula. It has been conventionally known that asolid electrolyte material having a perovskite type structure, such asLa_(2/3-x)Li_(3x)TiO₃, has high Li ion conductivity. However, withregard to a compound such as La_(2/3-x)Li_(3x)TiO₃, the problem is thatlithium content in the compound is so low that carrier concentration forcontributing to Li ion conduction is low and consequently sufficient Liion conductivity may not be obtained. On the contrary, a solidelectrolyte material of the present invention has so high lithiumcontent as to have the advantage that Li ion conductivity is high.

FIG. 1 is a ternary view explaining a solid electrolyte material of thepresent invention. With regard to a solid electrolyte material of thepresent invention, as shown in the above-mentioned general formula, partor all of La and part or all of Ti may be substituted with other metals(M1, M2); yet, in FIG. 1, the case where the solid electrolyte materialis an Li—La—Ti—O-based solid electrolyte material is described forconvenience. A solid electrolyte material of the present invention isshown by the area A in FIG. 1. On the other hand, the solid electrolytematerial described in Patent Literature 1 has a composition shown by thearea B in FIG. 1 when numerical ranges of x, y, and z are shown in theternary view. Similarly, the solid electrolyte material described inPatent Literature 2 has a composition shown by the line segment C inFIG. 1. The composition area (the area A) in the present inventiondiffers completely from the composition areas shown by the area B andthe line segment C.

A solid electrolyte material of the present invention is represented bya general formula: Li_(x)(La_(1-a)M1_(a))_(y) (Ti_(1-b)M2_(b))_(z)O_(δ).In the above-mentioned general formula, “x”, “y”, and “z” satisfyrelations of 0.850≦x/(x+y+z)≦0.930, and 0.087≦y/(y+z)≦0.115.

Further, in the above-mentioned general formula, “a” is 0≦a≦1, andpreferably 0≦a≦0.5. Similarly, in the above-mentioned general formula,“b” is 0≦b≦1, and preferably 0≦b≦0.5. In the present invention, “a” or“b” may be 0, and “a” and “b” may be 0.

Further, in the above-mentioned general formula, “δ” is 0.8≦δ≦1.2. Inconsideration of valences of metallic elements included in theabove-mentioned general formula, the value of δ may be specified by theelectroneutrality principle; yet, oxygen deficiency and oxygen excessmay be actually caused. Thus, in the present invention, the range of δis prescribed at 0.8≦δ≦1.2 in consideration of oxygen deficiency andoxygen excess.

Further, in the above-mentioned general formula, “M1” is a metal capableof being located at the same site as La in a crystal structure;specifically, at least one selected from the group consisting of Sr, Na,Nd, Pr, Sm, Gd, Dy, Y, Eu, Tb, and Ba.

Further, in the above-mentioned general formula, “M2” is a metal capableof being located at the same site as Ti in a crystal structure;specifically, at least one selected from the group consisting of Mg, W,Mn, Al, Ge, Ru, Nb, Ta, Co, Zr, Hf, Fe, Cr, and Ga.

A solid electrolyte material of the present invention may be amorphousor crystalline. The case of being amorphous has the advantage thatresistance increase in a grain boundary may be prevented. On the otherhand, the case of being crystalline has the advantage that Li ionconductivity in a crystal grain is high. In addition, in the presentinvention, the use of the after-mentioned reactive deposition methodallows crystal grains to be favorably joined to each other and allowsresistance increase in a grain boundary to be restrained even in thecase of being crystalline.

Further, a solid electrolyte material of the present inventionpreferably shows peaks in an X-ray diffraction measurement using CuKαwhere 2θ=22°, 27°, 34°, 35°. The reason therefor is that these peaks areconceived to derive from a crystal phase of high Li ion conductivity.This crystal phase does not belong to a conventional perovskite typestructure, as described in the after-mentioned Examples.

Further, a solid electrolyte material of the present invention may bebulky or in thin film form, and preferably in thin film form. The reasontherefor is that the use of the after-mentioned reactive depositionmethod allows a minute solid electrolyte material to be obtained andallows Li ion conductivity to be improved.

The size of a solid electrolyte material of the present invention is notparticularly limited. Above all, in the case where a solid electrolytematerial of the present invention is in thin film form, the thickness ofthe thin film is preferably 200 nm or more, more preferably 500 nm ormore, and far more preferably 800 nm or more. On the other hand, thethickness of the thin film is preferably 5 μm or less, more preferably 3μm or less, and far more preferably 2 μm or less.

A solid electrolyte material of the present invention may be used foroptional uses in which Li ion conductivity is required. Examples of theuses of the solid electrolyte material include batteries such as alithium battery and sensors such as a gas sensor. A method of producinga solid electrolyte material of the present invention is described indetail in the after-mentioned “C. Method of producing solid electrolytematerial”. A solid electrolyte material in a bulk body may be producedby using a mechanical milling method and a solid phase method, forexample.

B. Lithium Battery

Next, a lithium battery of the present invention is described. A lithiumbattery of the present invention is a lithium battery comprising: acathode active material layer containing a cathode active material, ananode active material layer containing an anode active material, and asolid electrolyte layer formed between the cathode active material layerand the anode active material layer, characterized in that the solidelectrolyte layer contains the above-mentioned solid electrolytematerial.

According to the present invention, the use of the above-mentioned solidelectrolyte material allows a high-output lithium battery.

FIG. 2 is a schematic cross-sectional view showing an example of alithium battery of the present invention. A lithium battery 10 in FIG. 2comprises: a cathode active material layer 1 containing a cathode activematerial, an anode active material layer 2 containing an anode activematerial, a solid electrolyte layer 3 formed between the cathode activematerial layer 1 and the anode active material layer 2, a cathodecurrent collector 4 for performing current collecting of the cathodeactive material layer 1, an anode current collector 5 for performingcurrent collecting of the anode active material layer 2, and a batterycase 6 for storing these members. The present invention is greatlycharacterized in that the solid electrolyte layer 3 contains the solidelectrolyte material described in the above-mentioned “A. Solidelectrolyte material”.

A lithium battery of the present invention is hereinafter described ineach constitution.

1. Solid Electrolyte Layer

A solid electrolyte layer in the present invention is first described. Asolid electrolyte layer in the present invention contains theabove-mentioned solid electrolyte material. The range of the thicknessof the solid electrolyte layer is preferably the same as the range ofthe thickness of the above-mentioned solid electrolyte material.

2. Cathode Active Material Layer

Next, a cathode active material layer in the present invention isdescribed. A cathode active material layer in the present invention is alayer containing at least a cathode active material, and may contain atleast one of a conductive material, a solid electrolyte material and abinder, as required. Examples of the cathode active material includeLiCoO₂, LiMnO₂, Li₂NiMn₃O₈, LiVO₂, LiCrO₂, LiFePO₄, LiCoPO₄, LiNiO₂ andLiNi_(1/3)Co_(1/3)Mn_(1/3)O₂.

A cathode active material layer in the present invention may furthercontain a conductive material. The addition of the conductive materialallows conductivity of the cathode active material layer to be improved.Examples of the conductive material include acetylene black, Ketj enBlack and carbon fiber. Further, the cathode active material layer mayfurther contain a solid electrolyte material. The addition of the solidelectrolyte material allows Li ion conductivity of the cathode activematerial layer to be improved. Examples of the solid electrolytematerial include an oxide solid electrolyte material and a sulfide solidelectrolyte material. Further, the cathode active material layer mayfurther contain a binder. Examples of the binder include afluorine-containing binder such as polytetrafluoroethylene (PTFE). Thethickness of the cathode active material layer is preferably within arange of 0.1 μm to 1000 μm, for example.

3. Anode Active Material Layer

Next, an anode active material layer in the present invention isdescribed. An anode active material layer in the present invention is alayer containing at least an anode active material, and may contain atleast one of a conductive material, a solid electrolyte material and abinder, as required. Examples of the anode active material include ametal active material and a carbon active material. Examples of themetal active material include In, Al, Si, and Sn. On the other hand,examples of the carbon active material include mesocarbon microbeads(MCMB), high orientation property graphite (HOPG), hard carbon and softcarbon.

A conductive material, a solid electrolyte material and a binder usedfor the anode active material layer are the same as the case of theabove-mentioned cathode active material layer. The thickness of theanode active material layer is preferably within a range of 0.1 μm to1000 μm, for example.

4. Other Constitutions

A lithium battery of the present invention has at least theabove-mentioned solid electrolyte layer, cathode active material layerand anode active material layer; and generally further has a cathodecurrent collector for performing current collecting of the cathodeactive material layer and an anode current collector for performingcurrent collecting of the anode active material layer. Examples of amaterial for the cathode current collector include SUS, aluminum,nickel, iron, titanium and carbon, and preferably SUS among them. On theother hand, examples of a material for the anode current collectorinclude SUS, copper, nickel and carbon, and preferably SUS among them.The factors such as thickness and shape of the cathode current collectorand the anode current collector are preferably selected properly inaccordance with usages of a lithium battery. A battery case of a generallithium battery may be used for a battery case used for the presentinvention. Examples of the battery case include a battery case made ofSUS.

5. Lithium Battery

A lithium battery of the present invention may be a primary battery or asecondary battery, and preferably a secondary battery among them. Thereason therefor is to be repeatedly chargeable and dischargeable and beuseful as a car-mounted battery, for example. Examples of the shape of alithium battery of the present invention include a coin shape, alaminate shape, a cylindrical shape and a rectangular shape. A method ofproducing a lithium battery of the present invention is not particularlylimited if it is a method for allowing the above-mentioned lithiumbattery, and the same method as a method of producing a general lithiumbattery may be used. Examples thereof include a method such that amaterial composing a cathode active material layer, a material composinga solid electrolyte layer and a material composing an anode activematerial layer are sequentially pressed to thereby produce a powergenerating element and this power generating element is stored inside abattery case, which is crimped.

C. Method of Producing Solid Electrolyte Material

Next, a method of producing a solid electrolyte material of the presentinvention is described. A method of producing a solid electrolytematerial of the present invention comprises steps of: preparing a rawmaterial, in which the raw material is made of Li, La, Ti, M1 (M1 beingat least one selected from the group consisting of Sr, Na, Nd, Pr, Sm,Gd, Dy, Y, Eu, Tb, and Ba), and M2 (M2 being at least one selected fromthe group consisting of Mg, W, Mn, Al, Ge, Ru, Nb, Ta, Co, Zr, Hf, Fe,Cr, and Ga); and forming a thin film, in which the solid electrolytematerial is formed using the raw material to a substrate by a reactivedeposition method using oxygen, and the solid electrolyte material isrepresented by a general formula:Li_(x)(La_(1-a)M1_(a))_(y)(Ti_(1-b)M2_(b))_(z)O_(δ), in which “x”, “y”,and “z” satisfy relations of x+y+z=1, 0.850≦x/(x+y+z)≦0.930, and0.087≦y/(y+z)≦0.115; “a” is 0≦a≦1; “b” is 0≦b≦1; and “δ” is 0.8≦δ≦1.2.

According to the present invention, the use of the reactive depositionmethod allows a minute thin film to be formed, and a solid electrolytematerial having excellent Li ion conductivity may be obtained by theabove-mentioned general formula.

FIG. 3 is a schematic cross-sectional view showing an example of amethod of producing a solid electrolyte material of the presentinvention. In FIG. 3, a crucible 12 in which Li metal, La metal and Timetal are put, and a substrate 13 are first placed in a chamber 11.Next, the pressure of the chamber 11 is reduced to form a vacuum state.Thereafter, O₂ plasma is caused to simultaneously volatilize Li metal,La metal and Ti metal by a resistance heating method and an electronbeam method. Thus, an LiLaTiO thin film 14 is deposited on the substrate13. A thin film with high amorphous nature is obtained if the substrateis not heated during the deposition, and a thin film with highcrystallinity is obtained by heating the substrate during the depositionor post-heating a thin film deposited on the substrate.

A method of producing a solid electrolyte material of the presentinvention is hereinafter described at each step.

1. Step of Preparing Raw Material

A step of preparing a raw material in the present invention is firstdescribed. The step of preparing a raw material in the present inventionis a step of preparing a raw material, in which the raw material is madeof Li, La, Ti, M1 (M1 being at least one selected from the groupconsisting of Sr, Na, Nd, Pr, Sm, Gd, Dy, Y, Eu, Tb, and Ba), and M2 (M2being at least one selected from the group consisting of Mg, W, Mn, Al,Ge, Ru, Nb, Ta, Co, Zr, Hf, Fe, Cr, and Ga).

In the present invention, elemental metals of Li, La, Ti, M1 and M2 aregenerally prepared. These elemental metals are preferably high inpurity. The reason therefor is to allow a solid electrolyte materialwith fewer impurities. Further, generally, M1 is not used in the case ofobtaining a solid electrolyte material such that “a” in theabove-mentioned general formula is 0, and M2 is not used in the case ofobtaining a solid electrolyte material such that “b” in theabove-mentioned general formula is 0.

2. Step of Forming Thin Film

Next, a step of forming a thin film in the present invention isdescribed. The step of forming a thin film in the present invention is astep of forming the above-mentioned solid electrolyte material whileusing the above-mentioned raw material to a substrate by a reactivedeposition method using oxygen.

In the present invention, the solid electrolyte material is formed by areactive deposition method. In this method, the thin-film solidelectrolyte material is formed by volatilizing the raw material to reactthe volatilized raw material with oxygen. Examples of a method ofvolatilizing the raw material include a resistance heating method and anelectron beam method. Examples of a method of reacting the volatilizedraw material with oxygen include a method of using oxygen plasma and amethod of using oxygen gas. In addition, in the present invention, thereactive deposition is preferably performed in vacuo, and is preferablyperformed specifically in a vacuum of 1×10⁻¹⁰ mBar or less. The reasontherefor is that a minute thin film may be formed. The thickness of thesolid electrolyte material may be controlled by deposition time.

Further, in the present invention, the thin-film solid electrolytematerial is formed on the substrate. The substrate in the presentinvention is not particularly limited and preferably selected properlyin accordance with usages of the solid electrolyte material. Forexample, in the case of using the solid electrolyte material as a solidelectrolyte layer of a lithium battery, a member having a cathode activematerial layer or an anode active material layer is preferably used asthe substrate.

3. Others

A solid electrolyte material obtained by the present invention is thesame as the contents described in the above-mentioned “A. Solidelectrolyte material”; therefore, the description herein is omitted. Thepresent invention may provide a solid electrolyte material characterizedby being obtained by the above-mentioned method of producing a solidelectrolyte material.

The present invention is not limited to the above-mentioned embodiments.The above-mentioned embodiments are exemplification, and any is includedin the technical scope of the present invention if it has substantiallythe same constitution as the technical idea described in the claim ofthe present invention and offers similar operation and effect thereto.

EXAMPLES

The present invention is described more specifically while showingexamples hereinafter.

Example 1

Lithium metal (ribbon, a purity of 99.9%, manufactured by Sigma-AldrichCo. LLC.), lanthanum metal (a purity of 99.9%, manufactured bySigma-Aldrich Co. LLC.), and titanium metal (slug, a purity of 99.98%,manufactured by Alfa Aesar®) were first prepared as a raw material.Next, the lithium metal was put in a 40 cm³ crucible made of pyrolyticboron nitride (PBN) and placed in a chamber. Next, the lanthanum metaland the titanium metal were each put in a 40 cm³ crucible made ofpyrolytic graphite and placed in the chamber in the same manner. AnSi/SiO₂/Ti/Pt laminated body (manufactured by NOVA Electronic Materials,LLC.) was used as a substrate, a deposition area was determined at 0.785cm² (equivalent to φ 10 mm), and a distance from the raw material to thesubstrate was determined at 500 mm. Next, the inside of the chamber wassubject to a high vacuum of 1×10⁻¹⁰ mBar or less.

Thereafter, resistance heating (Knudsen Cells) was performed for thecrucible in which the lithium metal was put to volatilize the lithium,and simultaneously electron beam irradiation was performed for thecrucible in which the lanthanum metal was put and the crucible in whichthe titanium metal was put to volatilize the lanthanum metal and thetitanium metal. Oxygen plasma was caused in the chamber by using anoxygen plasma generator (manufactured by Oxford Applied Research Ltd.,RF source, HD25™) and reacted with the volatilized raw material tothereby obtain a thin-film solid electrolyte material on the substrate.The substrate was heated to a temperature of 700° C. during thedeposition.

The thickness of the obtained solid electrolyte material was 390 nm.When ICP analysis (inductively coupled plasma analysis) was performedfor the obtained solid electrolyte material, and a result ofLi:La:Ti=85.3:1.5:13.2 was offered.

Examples 2 to 5 and Comparative Examples 1 and 2

A thin-film solid electrolyte material was each obtained in the samemanner as Example 1 except for properly adjusting the amount of themetals volatilized from the crucible with a shutter. The compositions ofthe solid electrolyte materials obtained in Examples 2 to 5 andComparative Examples 1 and 2 at a ratio of Li:La:Ti was as shown in thefollowing table 1.

[Evaluation 1]

(1) X-Ray Diffraction Measurement

XRD measurement using CuKα was performed for the solid electrolytematerials obtained in Example 1 and Comparative Example 1. The result isshown in FIGS. 4 and 5. As shown in FIG. 4, it was confirmed that thesolid electrolyte material of Example 1 showed peaks where 2θ=22°, 27°,34°, 35°. These peaks did not belong to a perovskite type structureknown as an Li—La—Ti—O-based high ion conduction phase. Thus, it isconceived that the solid electrolyte material of Example 1 has astructure except the perovskite type structure. On the other hand, asshown in FIG. 5, it was confirmed that the solid electrolyte material ofComparative Example 1 showed great peaks where 2θ=32°, 39°, 46° and hadLi₂TiO₃ and LiTi₂O₄ as main components through these peaks. Li₂TiO₃ andLiTi₂O₄ are known as compounds with low Li ion conductivity.

(2) Li Ion Conductivity

Li ion conductivity of the solid electrolyte materials obtained inExamples 1 to 5 and Comparative Examples 1 and 2 was evaluated. Platinumwas first deposited on the surface of the solid electrolyte materialformed on the substrate to produce a symmetrical cell of Pt/solidelectrolyte material/Pt. Next, an alternating current impedance methodwas performed at a temperature of 25° C. to calculate Li ionconductivity. The result is shown in table 1 and FIG. 6.

TABLE 1 Li/(Li + La/ log(σ ion/ Li La Ti La + Ti) (La + Ti) Scm⁻¹)Example 1 85.3 1.5 13.2 0.853 0.102 −3.87 Example 2 86.3 1.4 12.3 0.8630.102 −3.39 Example 3 88.4 1.2 10.4 0.884 0.103 −3.20 Example 4 91.6 0.97.5 0.916 0.107 −3.01 Example 5 93.0 0.7 6.3 0.930 0.100 −3.74Comparative 84.4 1.6 14.0 0.844 0.103 −6.28 Example 1 Comparative 93.60.7 5.8 0.935 0.108 −5.56 Example 2

As shown in table 1, Examples 1 to 5 and Comparative Examples 1 and 2were all fixed in the vicinity of La/(La+Ti)=0.103. Further, as shown inFIG. 6, Li ion conductivity was remarkably high in Examples 1 to 5 ascompared with Comparative Examples 1 and 2. In addition, when the resultof table 1 and FIG. 6 was represented by a ternary view, as shown inFIG. 7, it was confirmed that excellent Li ion conductivity was obtainedwhen Li/(Li+La+Ti) satisfied 0.850≦Li/(Li+La+Ti)≦0.930.

Examples 6 to 9 and Comparative Examples 3 and 4

A thin-film solid electrolyte material was each obtained in the samemanner as Example 1 except for properly adjusting the amount of themetals volatilized from the crucible with a shutter. The compositions ofthe solid electrolyte materials obtained in Examples 6 to 9 andComparative Examples 3 and 4 at a ratio of Li:La:Ti were as shown in thefollowing table 2.

[Evaluation 2]

Li ion conductivity of the solid electrolyte materials obtained inExamples 4, 6 to 9 and Comparative Examples 3 and 4 was evaluated. Theevaluation method is the same as the above. The result is shown in table2 and FIG. 8.

TABLE 2 Li/(Li + La/ log(σ ion/ Li La Ti La + Ti) (La + Ti) Scm⁻¹)Example 4 91.6 0.9 7.5 0.916 0.107 −3.01 Example 6 91.5 0.8 7.7 0.9150.094 −4.01 Example 7 91.4 0.8 7.8 0.914 0.093 −3.89 Example 8 91.8 0.97.3 0.918 0.110 −3.64 Example 9 91.3 1.0 7.7 0.913 0.115 −3.35Comparative 91.6 0.6 7.8 0.916 0.071 −6.39 Example 3 Comparative 91.51.0 7.5 0.915 0.118 −5.95 Example 4

As shown in table 2, Examples 4, 6 to 9 and Comparative Examples 3 and 4were all fixed in the vicinity of Li/(Li+La+Ti)=0.916. Further, as shownin FIG. 8, Li ion conductivity was remarkably high in Examples 4, 6 to 9as compared with Comparative Examples 3 and 4. In addition, when theresult of table 2 and FIG. 8 was represented by a ternary view, as shownin FIG. 9, it was confirmed that excellent Li ion conductivity wasobtained when La/(La+Ti) satisfied 0.087≦La/(La+Ti)≦0.115.

Examples 10 to 15 and Comparative Examples 5 to 9

A thin-film solid electrolyte material was each obtained in the samemanner as Example 1 except for properly adjusting the amount of themetals volatilized from the crucible with a shutter. The compositions ofthe solid electrolyte materials obtained in Examples 10 to 15 andComparative Examples 5 to 9 at a ratio of Li:La:Ti were as shown in thefollowing table 3.

[Evaluation 3]

Li ion conductivity of the solid electrolyte material obtained inExamples 10 to 15 and Comparative Examples 5 to 9 was evaluated. Theevaluation method is the same as the above. The result is shown in table3.

TABLE 3 Li/(Li + La/ log(σ ion/ Li La Ti La + Ti) (La + Ti) Scm⁻¹)Example 10 85.0 1.4 13.6 0.850 0.093 −3.63 Example 11 85.1 1.3 13.60.851 0.087 −3.39 Example 12 85.4 1.6 13.0 0.854 0.110 −3.55 Example 1390.1 1.1 8.8 0.901 0.111 −3.87 Example 14 90.9 0.8 8.3 0.909 0.088 −3.74Example 15 93.0 0.8 6.2 0.930 0.114 −3.56 Comparative 81.2 1.7 17.10.812 0.090 −6.53 Example 5 Comparative 82.1 2.1 15.8 0.821 0.117 −5.93Example 6 Comparative 84.4 1.9 13.7 0.844 0.122 −5.24 Example 7Comparative 93.6 0.4 6.0 0.936 0.063 −4.39 Example 8 Comparative 93.60.8 5.6 0.936 0.125 −4.96 Example 9

As shown in table 3, Li ion conductivity was remarkably high in Examples10 to 15 as compared with Comparative Examples 5 to 9. In addition, whenthe result of table 3 was represented by a ternary view, as shown inFIG. 10, it was confirmed that excellent Li ion conductivity wasobtained when Li/(Li+La+Ti) satisfied 0.850≦Li/(Li+La+Ti)≦0.930 andLa/(La+Ti) satisfied 0.087≦La/(La+Ti)≦0.115.

Reference Signs List 1 cathode active material layer 2 anode activematerial layer 3 solid electrolyte layer 4 cathode current collector 5anode current collector 6 battery case 10 lithium battery 11 chamber 12crucible 13 substrate 14 LiLaTiO thin film

The invention claimed is:
 1. A solid electrolyte material represented bya general formula:Li_(x)(La_(1-a),M1_(a))_(y)(Ti_(1-b)M2_(b))_(z)O_(δ), wherein “x”, “y”,and “z” satisfy relations of x+y+z=1, 0.850≦x/(x+y+z)≦0.930, and0.087≦y/(y+z)≦0.115; “a” is 0≦a≦1; “b” is 0≦b≦1; “δ” is 0.8≦δ≦1.2; “M1”is at least one selected from the group consisting of Sr, Na, Nd, Pr,Sm, Gd, Dy, Y, Eu, Tb, and Ba; and “M2” is at least one selected fromthe group consisting of Mg, W, Mn, Al, Ge, Ru, Nb, Ta, Co, Zr, Hf, Fe,Cr, and Ga.
 2. The solid electrolyte material according to claim 1,wherein the solid electrolyte material shows peaks in a X-raydiffraction measurement using CuKα where 2θ=22°, 27°, 34°, 35°.
 3. Thesolid electrolyte material according to claim 1, wherein the solidelectrolyte material is in thin film form.
 4. The solid electrolytematerial according to claim 1, wherein the solid electrolyte materialhas a thickness of 200 nm to 5 μm.
 5. The solid electrolyte materialaccording to claim 1, wherein the “a” and the “b” are
 0. 6. A lithiumbattery comprising: a cathode active material layer containing a cathodeactive material, an anode active material layer containing an anodeactive material, and a solid electrolyte layer formed between thecathode active material layer and the anode active material layer,wherein the solid electrolyte layer contains the solid electrolytematerial of claim
 1. 7. A method of producing a solid electrolytematerial comprising steps of: preparing a raw material, in which the rawmaterial is made of Li, La, Ti, M1 (M1 being at least one selected fromthe group consisting of Sr, Na, Nd, Pr, Sm, Gd, Dy, Y, Eu, Tb, and Ba),and M2 (M2 being at least one selected from the group consisting of Mg,W, Mn, Al, Ge, Ru, Nb, Ta, Co, Zr, Hf, Fe, Cr, and Ga); and forming athin film, in which a solid electrolyte material is formed using the rawmaterial to a substrate by a reactive deposition method using oxygen,and the solid electrolyte material is represented by a general formula:Li_(x)(La_(1-a)M1_(a))_(y)(Ti_(1-b)M2_(b))_(z)O_(δ), in which “x”, “y”,and “z” satisfy relations of x+y+z=1, 0.850≦x/(x+y+z)≦0.930, and0.087≦y/(y+z)≦0.115; “a” is 0≦a≦1; “b” is 0≦b≦1; and “δ” is 0.8≦δ≦1.2.8. The method of producing a solid electrolyte material according toclaim 7, wherein the solid electrolyte material shows peaks in a X-raydiffraction measurement using CuKα where 2θ=22°, 27°, 34°, 35°.
 9. Themethod of producing a solid electrolyte material according to claim 7,wherein the solid electrolyte material has a thickness of 200 nm to 5μm.
 10. The method of producing a solid electrolyte material accordingto claim 7, wherein the solid electrolyte material is formed in the thinfilm forming step by the reactive deposition method using an oxygenplasma.
 11. The method of producing a solid electrolyte materialaccording to claim 7, wherein the substrate is a member containing acathode active material layer or an anode active material layer.